Chapter 7
METAMORPHIC ROCKS|
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Chapter 7 METAMORPHIC ROCKS |
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C. CHANGES IN TEXTURE AND MINERALOGY |
A glacier deposited gneiss boulder, Newfoundland, Canada. Canadian Geological Society. |
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28. SCHIST |
31. QUARTZITE |
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29. GNIESS |
32. SLATE |
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30. MARBLE |
From the Greek work "schistos" meaning "easily cleft".
A coarse-grained and foliated metamorphic rock with sub-parallel orientation of the platy or prismatic minerals which cominate its composition.
Light to dark in color.
The common minerals which give rise to schistosity are the micas in the platy schists and amphiboles in the linear schists.
Schists are named according to their most prominent minerals, e.g. garnet-mica schist, hornblende schist.
Garnet is a common mineral.
Banded rock (dark colored and light colored minerals) formed during high-grade metamorphism.
The thickness of the bands may vary from a millimeter or so up to several centimeters and may or may not be consistent throughout the rock.
Gneiss is generally a coarse-grained rock.
From the Greek word "marmoros" meaning "a white, glistening stone".
A metamorphic rock composed essentially of the mineral calcite (CaCO3).
Produced by recrystallization through thermal (contact) and regional metamorphism.
Marbles derived from pure limestones consist simply of recrystallized calcite.
Impurities in the form of dolomite, silica, iron compounds, and clay minerals may give rise to other minerals which give certain marbles their characteristic appearance.
Used as architectural or ornamental stone.
From the German provincial "quarz".
Finely to coarsely crystalline.
Sometimes looks like sandstone but is denser than sandstone.
An excellent constructional rock because it is very strong and resistant to weathering.
From the Old French work "esclat" meaning "a splinter".
A fine-grained, low-grade metamorphic rock that has undergone little recrystallization and that possesses a well developed fissility (slaty cleavage).
When slate is produced by thermal metamorphism, it may develop spots of new minerals or recognizable crystals of new minerals such as pyrite.
More compact than shale.
Used as roofing tile and as a writing tablet or "blackboard".
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